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NRC proposes changes to its rules on nuclear materials
In response to Executive Order 14300, “Ordering the Reform of the Nuclear Regulatory Commission,” the NRC is proposing sweeping changes to its rules governing the use of nuclear materials that are widely used in industry, medicine, and research. The changes would amend NRC regulations for the licensing of nuclear byproduct material, some source material, and some special nuclear material.
As published in the May 18 Federal Register, the NRC is seeking public comment on this proposed rule and draft interim guidance until July 2.
N. Authier, J. P. Both, J. C. Nimal
Nuclear Science and Engineering | Volume 137 | Number 2 | February 2001 | Pages 146-155
Technical Paper | doi.org/10.13182/NSE01-A2181
Articles are hosted by Taylor and Francis Online.
New biasing sampling schemes for the "once-more-collided-flux-at-a-point" method for gamma calculations are studied. This technique, designed by Kalos, Steinberg, Kalli, and Cashwell, for neutron point flux estimation cannot be directly applied to photon transport problems. Because of the different interaction processes, it is shown that even if the mean and second moment remain bounded, very large variations of the scoring weights occur for specific collision deviations, which leads again to jumps of mean and variance. Two biasing methods are proposed for the resampled postcollision direction and the next deterministic collision to treat the anisotropic behavior of the coherent scattering that is the main cause of instability. The method is tested on an MCNP4A benchmark. This new treatment of the point flux estimation has been integrated in the TRIPOLI-4 Monte Carlo code. Note that no bias results are achieved with CPU costs, which reserves this method for reference calculations.